Crash stop and magnetic latch for a voice coil actuator

ABSTRACT

A magnetic latch for holding a head positioner assembly within a disc drive system. The disc drive system has a head positioning apparatus located within a housing for positioning a plurality of read/write heads relative to a recording media within the housing. The head positioning assembly carries a voice coil motor for precisely controlling the movements of the head positioner assembly. The magnetic latch is positioned within a bumper stop that limits the head positioners movement to hold the head positioner assembly in an orientation where the heads can be effectively parked without damaging the recording media.

The present invention relates generally to an improved latchingarrangement for head positioner assemblies within information storagesystems such as disc drives. More particularly, the invention relates toa magnetic latch for securing rotatable head positioner assemblies inplace when the disc drives is not in use.

BACKGROUND OF THE INVENTION

Disc drive machines record and reproduce information on a recordingmedia. The media generally takes the form of circular informationstorage discs having a multiplicity of concentric tracks. ConventionalWinchester type disc drives include a plurality of vertically alignedrotating information storage discs, each having at least one associatedmagnetic head that is adapted to transfer information between the discand an external system. Each head is carried by an elongated flexurearm. The flexure arms are vertically aligned and are each attached to acommon head positioner assembly. The head positioner assembly is adaptedto move the heads back and forth in unison across the face of thevertically aligned discs. The head positioner assembly may be eitherrotationally mounted, or may take the form of a linear carriage that isfree to move back and forth along a single axis. In rotary mounted headpositioner assemblies, a voice coil motor rotates the head positionerassembly about a pivot mechanism to precisely position the headsrelative to the magnetic discs.

Due to the precise positioning requirements of the read/write heads, thehead positioner assembly must be finely balanced and the pivot mechanismmust offer high precision and reliability in order to minimizeundesirable vibrations within the drive. New drives constantly push forhigher access speed and more memory storage within a confined space. Inhigh speed compact disc drives, such as the 31/2 inch drives nowbecoming popular, if any of the drive's components have primary resonantfrequencies under approximately 5 Khz, mechanical movement within thedrive will occasionally excite the resonant frequencies during normaloperation which can limit the drives performance and/or generateundesirable noise which gives the appearance of an inferior qualityproduct.

When the disc drive is not in use, it is important to "park" the headsin a position where they will not either mechanically or electricallyinterfere with the information storage media. The head positionerassembly must be held in place even when the drive is dropped, struck orotherwise mishandled. To hold the head positioner assembly (and thus theheads) in place while the drive is not in use, a latching arrangement istypically provided. One common latching arrangement utilizes aselectively actuatable solenoid to hold the head positioner assembly inplace, however, such systems have several drawbacks including the needfor supporting electronics, relying on moving parts, occupying largespaces and/or detracting from the balance of the head positionerassembly.

SUMMARY OF THE INVENTION

Accordingly, it is a primary objective of the present invention toprovide an effective head positioner assembly latching arrangement thathas a low part count and is easy to assemble at low costs.

Another objective is to provide a latching arrangement that does noteffect the balance of the head positioner assembly.

Another objective of the invention is to provide a magnetic latching fora head positoner assembly.

To achieve the foregoing and other objects and in accordance with thepurpose of the present invention, a magnetic latch is provided for adisc drive system having a head positioning assembly for positioning aplurality of transducer heads relative to a recording media locatedwithin a disc housing. The magnetic latch includes a bumper stop, astrike plate and magnet means. The bumper stop limits the headpositioning assembly's movement in one direction. The magnet means iscarried by the bumper stop for magnetically engaging the strike plate tolatch the head positioner assembly against the bumper stop when thedrive is not in use, the magnet means including a slidable element thatis slidably coupled to the bumper stop to insure that the magnet meansfirmly engages the strike plate. The strike plate, which is formed of amagnetic material, is carried by the head positioner assembly.

BRIEF DESCRIPTION OF THE DRAWINGS

The features of the present invention that are believed to be novel areset forth with particularity in the appended claims. The invention,together with further objects and advantages thereof, may best beunderstood by reference to the following description taken inconjunction with the accompanying drawings in which:

FIG. 1 is a top view of a disc drive that incorporates the presentinvention with its upper casing removed.

FIG. 2 is a side view of the disc drive shown in FIG. 1.

FIG. 3 is an exploded perspective view of a voice coil motor suitablefor driving a rotary head positioner assembly.

FIG. 4 is an exploded perspective view of a magnetic latch fabricated inaccordance with the present invention.

FIG. 5 is a back view of the magnetic latch shown in FIG. 4.

FIG. 6 is a an exploded perspective view of a bumper stop.

FIG. 7 is an end view of the coil and strike plate for the voice coilmotor shown in FIG. 3.

DETAILED DESCRIPTION OF THE DRAWINGS

Referring first to FIGS. 1 & 2, a rotary disc drive system suitable forincorporating the teaching of the present invention is shown indiagrammatic form. A plurality of magnetic information storage discs 20are journaled about a spindle motor assembly 30 within a housing 5having upper and lower casing members 7 & 9 respectively. Each magneticdisc 20 has a multiplicity of concentric circular information storagetracks for recording information. Spacers 23 are disposed betweenadjacent information storage discs 20 to maintain their spacing and adisc clamp 25 positioned above the top information storage disc 21firmly secures the magnetic discs 20 the spindle motor assembly 30.

A head positioner assembly 40 includes a pivot housing 42 that isrotationally coupled between the upper and lower casings 7, 9 in onecorner of the housing 5 by pivot bearing 44. The head positionerassembly 40 carries a plurality of head arm flexures 50 that each carrya magnetic read/write onto the magnetic discs 20. The head positionerassembly 40 also carries a servo arm 54 which carries a servo head 55for accurately positioning the magnetic heads 52 relative to theinformation storage racks. The head and servo arms are each attached tothe head positioner assembly 40 by individual flexure mounts 58. A voicecoil motor 60 is adapted to precisely rotate the head positionerassembly back and forth such that the magnetic and servo heads movetogether across the magnetic discs. A magnetic latch 70 holds the headpositioner assembly in place when the disc drive is not in use. Therotational movements of the pivot housing 42 are limited by bumper stops80 which are disposed directly behind the voice coil motor 60.

The head positioner assembly 40 includes a pivot housing 42 that isjournaled about pivot mechanism 44. The pivot housing is somewhat Eshaped and has a plurality of forwardly extending vertically alignedplatforms that each form a mounting base for a single flexure mount 58.The coil 64 for voice coil motor 60 is attached to the back side of thepivot housing 42 by a single center screw 107. To minimize weight at areasonable cost, the pivot housing 42 is fabricated from aluminum. Ascan be appreciated by reference to FIG. 1, in the preferred embodiment,the pivot housing 42 as well as almost everything it carries aresymmetrical about its longitudinal axis. The symmetry is desirable toprecisely balance the head positioning assembly, which reducesundesirable internal vibrations.

A 32 pin connector 150 serves as the communications port between thedisc drive and an external computer system. Two printed circuit cables(PCCs) are coupled between the connector 150 and the pivot housing 42.Electrical communications between the disc controller and the voice coilmotor 60 are made over a drive PCC 90. Communications between the dataand servo heads 52, 55 and the system controller are made over aread/write PCC 95. To more closely mechanically balance the headpositioner assembly, drive PCC 90 and read/write PCC 95 are crossed suchthat they bias the pivot housing 42 in opposite directions, therebyreducing the parasitic torque on the system. The crossed nature of theprinted circuit cables also reduces noise generated from electricalinterference between the cables.

Referring next to FIG. 3, the voice coil motor 60 includes a center pole62 having coil 64 journaled thereabout in a spaced apart relation. Outerpoles 66 are sandwiched over the top and bottom sides of the coil 64 andare sized so as to allow coil 64 to move freely back and forth over theinner pole within the confines set by bumper stops 80. The outer polesare identical in construction.

A strike plate 100 is mounted to the back side of coil 64 as shown inFIG. 7. The strike plate forms a contact surface for both magnetic latch70 and bumper stops 80. Since the strike plate 100 is the contactsurface for the magnetic latch, it must be formed of a magnetic materialsuch as magnetic stainless steel. A support member 105 is coupled to thefront surface of coil 64 to form an attachment plate for the pivothousing 42. The pivot housing may be firmly secured to the supportmember 105 via screw 107. Strike plate 100 and support member 105 may bebonded to the coil using a suitable epoxy.

When the disc drive is not in use, it is important to park the heads ina position where they will not either mechanically or electricallyinterfere with the information storage media. The head positionerassembly must be held in place even when the drive is dropped, struck orotherwise mishandled. To hold the head positioner assembly (and thus theheads) in place while the drive is not in use, a magnetic latch 70 isprovided in one of the bumper stops 80 that limit the rotationalmovements of the head positioner assembly. Specifically, the innerbumper stop 81 is positioned such that when strike plate 100 restsagainst it, the heads will be located adjacent the spindle motorassembly 30 spaced apart from the spacers 23 that are journaled aboutthe spindle motor assembly. The second bumper stop 82 is positioned suchthat the heads will be outside of the outermost information storagetrack on the discs 20 when strike plate 100 rests against bumper stop82.

Referring next to FIG. 6, bumper stop 82 includes bumper pad 84 disposedwithin a frame 86 that is securely fastened to the lower casing 9. Thebumper pad is formed from a resilient material such as rubber and ispress fit into a recess 87 within the frame 86. The leading edge of thebumper pad 84 forms its contact surface 85.

Referring ext to FIGS. 4 and 5, the embodiment of the magnetic latchchosen for the purpose of illustration will be described. The magneticlatch 70 includes upper and lower magnetic poles 71 and 72 respectivelythat are disposed about magnet 74. Poles 71 and 72 are substantially "L"shaped, having an extended portion 76 and a catch portion 77. The magnet74 is rectangular. The poles extend slightly beyond the magnet 74 toprevent the magnet from being hit by strike plate 100. It should beappreciated that the poles are independently slidable so that they canreadily engage strike plate 100 without any air gaps when the strikeplate is in contact with the magnetic latch 70.

The bumper stop 81 is virtually identical to bumper stop 82 except thatthe bumper pad 88 within bumper stop 81 has a recess 89 therein. Themagnetic latch 70 is placed within the recess 89 in bumper pad 88 suchthat the extended portions of poles 71 and 72 extend beyond the contactsurface 85 of bumper pad 88. The poles 71, 72, as well as the magnet 74are loosely placed within the recess 89 with the catch portions 77 ofthe poles being arranged to limit the distance the poles can sliderelative to the bumper stop to prevent the magnetic latch from slippingout of the bumper stop. Since the poles are not connected together, theymay slide independently relative to the bumper stop.

It will be appreciated that the voice coil motor 60 must be designed togenerate sufficient torque to pull the strike plate 100 away from themagnetic latch 70. The magnet chosen as magnet 74 preferably has amagnetic field with a very flat profile. This is desirable to minimizethe effect that the latch has on the head positioner assembly when theheads are positioned over the information storage discs. By way ofexample, a suitable design strength for the magnetic latch is one inwhich the latch will withstand a 70 g shock pulse sustained diagonallyacross the drive.

In operation, the head positioner assembly will rest in a "home"position wherein magnetic latch 70 firmly hold the pivot housing inplace. When a command is received to access the disc, the voice coilmotor is activated to pull the strike plate away from the magnetic latchand position the heads as directed. After the requested functions havebeen executed, the head positioner assembly is returned to the homeposition until further directions are received.

The described latching structure has several advantages. Primarily itallows the pivot housing to be symmetrically balanced. An evenlybalanced head positioner assembly is very important to high speed discs.

Although only one embodiment of the present invention has been describedherein, it should be understood that the present invention may beembodied in many other specific forms without departing from the spiritor scope of the invention. Particularly, it should be appreciated thatthe actual configuration of the various disc drive components may bewidely varied. The construction of the magnetic latch as well as itsintegration into the bumper stop may be widely varied as well.Therefore, the present examples and embodiments are to be considered asillustrative and not restrictive, and the invention is not to be limitedto the details given herein, but may be modified within the scope of theappended claims.

I claim:
 1. A magnetic latch for a disc drive system having a head positioner assembly for positioning a plurality of transducer heads relative to a recording media located within a disc housing, the head positioner assembly being movable with respect to the disc housing, the magnetic latch including:a bumper stop fixably mounted to the housing for limiting the head positioner assembly's movement in one direction; a strike plate carried by the head positioner assembly that is formed of a magnetic material; and magnet means mounted to the bumper stop for magnetically engaging the strike plate to latch the head positioner assembly against the bumper stop when the drive is not in use, the magnet means including a slidable element that is slidably coupled to the bumper stop to insure that the magnet means firmly engages the strike plate.
 2. A magnetic latch for a disc drive system having a head positioner assembly for positioning a plurality of transducer heads relative to a recording media located within a disc housing, the magnetic latch including:a bumper stop for limiting the head positioner assembly's movement in one direction; the bumper stop having a recess therein, a strike plate carried by the head positioner assembly that is formed of a magnetic material; magnetic means carried by the bumper stop for magnetically engaging the strike plate to latch the head positioner assembly against the bumper stop when the drive is not in use, the magnet means including a slidable element that is slidably coupled to the bumper stop to ensure that the magnet means firmly engages the strike plate; a bumper pad disposed within said recess, wherein said bumper pad is formed of a resilient material and carries said magnetic means to cushions the impact of the strike plate when it strikes said magnetic means.
 3. A magnetic latch as recited in claim 2 wherein said magnetic means includes a magnet and a pair of independently slidable poles.
 4. A magnetic latch as recited in claim 3 further comprising a second bumper stop for limiting the head positioner assembly's movement in a second direction.
 5. A disc drive system comprising:a magnetic transducer head; a magnetic recording media; a head positioner assembly for positioning the transducer head relative to the recording media, the head positioner assembly including a pivot mechanism, a pivot housing that carries said transducer head, said pivot housing being journaled about the pivot mechanism, and a voice coil motor for rotating said pivot housing about said pivot mechanism, the voice coil motor having a center pole, a coil journaled about the center pole in a spaced apart relation and a pair of outer poles disposed on opposite sides of said coil; a bumper stop for limiting the head positioner assembly's movement in one direction, the bumper stop having a recess therein; a strike plate formed of a magnetic material, said strike plate being carried by the coil; magnet means carried by the bumper stop for magnetically engaging the strike plate to latch the head positioner assembly against the bumper stop when the drive is not in use, the magnet means including a magnet and a pair of independently slidable poles; and a bumper pad disposed within said recess, wherein said bumper pad is formed of a resilient material and carries said magnetic means to cushion the impact of the strike plate when it strikes said magnetic means. 